Air ride compressor woes …

[adventurenali92]

I have a Dorman compressor in my 2007 and it does *not* perform a self-test after each start but it works great when the rear end gets loaded up. I've read that it's because the rear suspension needs a calibration step done with a Tech 2 but I haven't bothered because it's working when I need it to. No need for a self-test at each startup, IMHO. It'll just wear the pump out faster.

Weird. I have a dorman unit and mine self tests at every start up. I can hear the vent open and then it runs for about 3ish seconds. I never did the relearn process. I just replaced it and went on my way…. Lol

 

[petethepug]

It all depends on what happens when the pump fails. The OE pumps don’t have thermal overload protection to shut off if they overheat.

The pumps can short out and die or run for months drawing overload which can ultimately ruin the software programming in the control module or BCM, wherever it’s located. Then it’ll need to be reflashed / reprogrammed if that’s the case.

 

[K2 Kaiju]

The compressor fires when the level sensor detects the rear is low. As the shocks age, they don't hold air as well, and the compressor fires every time you start up. With new shocks, you are probably holding air longer, and it doesn't need to fire. You can test by standing on your rear hitch or bumper when the engine is running...

 

[Geotrash]

The compressor fires when the level sensor detects the rear is low. As the shocks age, they don't hold air as well

Yes, this is correct to this point.

and the compressor fires every time you start up.

This part is not correct. The compressor performs a self-test after every engine start, regardless of pressure in the system. Here is a description of the operation of the system:

Automatic Level Control Description and Operation

The automatic level control (ALC) system maintains a desired rear suspension position under all types of towing, hauling, and loading conditions.

The system uses the electronic suspension control module (ESCM), ELC relay, ALC compressor assembly, air dryer, air lines, shock absorbers with integral air chambers, suspension position sensors, exhaust valve, driver information center (DIC), and the serial data circuit to perform the system functions.

When the vehicle is unloaded, the rear suspension is at a desired position, which is monitored by the ESCM using the position sensor signal voltage inputs. As weight is added to the rear of the vehicle, the position sensor's signal voltage inputs change. When the ESCM detects a steady substantial change in the position sensor signal voltages for at least 10 seconds, it responds by commanding ON the ELC relay, which activates the compressor causing the air pressure in the shock absorber chambers to inflate. This inflation raises the rear of the vehicle to regain the desired suspension position. When weight is removed from the vehicle, the ESCM responds by commanding ON the exhaust valve causing the air pressure in the shock absorber chambers to deflate. This deflation lowers the vehicle to regain the desired suspension position.

The compressor is a positive displacement piston air pump driven by a 12-volt DC permanent magnet motor. The compressor draws filtered air through an intake line attached to an under body rail. The compressed air is then run through a dryer containing a moisture-absorbing chemical that dries the compressed air before it is sent to the shock absorber chambers. Each time the compressor is activated, the ESCM commands ON the exhaust valve for 1.5 seconds to release air from the compression chamber in the compressor's cylinder head ensuring low motor current draw upon compressor activation. The ESCM also limits the amount of compressor run time to 255 seconds to protect the compressor components from thermal damage.

The system also performs a self test on each ignition ON cycle in which the ESCM commands the ELC relay ON, activating the compressor for 4 seconds then monitors the position sensor's signal voltage inputs to verify the compressor is functioning and the system is holding air pressure.

The ESCM has the ability to detect malfunctions within the ALC system. Any malfunctions detected will cause the DIC to display the SERVICE SUSPENSION SYSTEM message. For more information on other functions of the ESCM, refer to Electronic Suspension Control Description and Operation See: Electronic Suspension Control.

With new shocks, you are probably holding air longer, and it doesn't need to fire. You can test by standing on your rear hitch or bumper when the engine is running...

The reasons the compressor doesn't always fire on startup have to do with the system not being calibrated correctly. Other members here have reported that when their compressor did not perform the self-test after each engine start, that using a scan tool to calibrate the suspension restored normal operation.

 

[Trey Hardy]

Drive 2010 Escalade EsV

Timeline…

2020: shocks leaking and compressor died. Replaced both shocks with OEM and got a Dorman compressor.

2023: noticed compressor was not inflating when towing a boat. I could hear the solenoid click at the compressor, but then nothing. Got a warranty replacement compressor through rock auto. Installed the new compressor and everything worked fine. Now the day after I installed it, compressor doesn’t fire up when turning on the ignition and I don’t hear the solenoid click anymore at all. Checked all the fuses, all seem good. Only thing I haven’t checked is the relay because I just don’t think it would go bad in one day. Did my compressor crap out in one day? What would cause me to not hear that solenoid anymore? Help is appreciated, I’ve got 227k miles on this baby and plan to keep her forever but I’ve about had it with this air suspension bs.

I’ll tell you what to do… take the compressor and air shocks and go tie them to a rope then throw them overboard to use as an anchor for your boat. And throw some normal bilsteins up in there and be done with that junk

 

[Geotrash]

I’ll tell you what to do… take the compressor and air shocks and go tie them to a rope then throw them overboard to use as an anchor for your boat. And throw some normal bilsteins up in there and be done with that junk

Problem then is that the springs on ALC rigs are softer than regular rigs, so they will sag more with even a modest load. You'd have to swap everything out and it's not typically a troublesome system. Nothing better for trailer towing on the market, too. And I don't think the OP has anything wrong that a calibration won't fix, but even that's optional.

 

[gunslinger]

Thanks all. While at the boat ramp I did hear the compressor run. So it must just be the calibration as stated by several of you. Good to know the system is working as intended though. Standing on the back wasn’t able to get the compressor to run, I think because I already had a load of bricks in the back so it must have known it was fully inflated. I removed the bricks and think I heard a hiss of the air being released. Then the compressor was running at the boat ramp the next day.

I can tell the car sits level all the time now too. Thanks, feeling much better about it.

 

[Geotrash]

Thanks all. While at the boat ramp I did hear the compressor run. So it must just be the calibration as stated by several of you. Good to know the system is working as intended though. Standing on the back wasn’t able to get the compressor to run, I think because I already had a load of bricks in the back so it must have known it was fully inflated. I removed the bricks and think I heard a hiss of the air being released. Then the compressor was running at the boat ramp the next day.

I can tell the car sits level all the time now too. Thanks, feeling much better about it.

Awesome! Thanks for following up. Don't be a stranger now.

 

[ieastsidechevyrider]

Without s tech2 just pull an air line to drop pressure, reconnect and then start the truck. Should run.

Pull an air line while the truck is powered on and running?

 

[petethepug]

Whoa, 05 on the Orig z55 shows how well Delphi built them when the technology was new. Almost 20 years means you’ve gotten your money’s worth with the cush put on that land yacht.

I’ve got the Orig on my 09 Esky that are toasted. At almost 180k it’ll get a front suspension refresh when the the mag struts are replaced. I will say that our 06 Denali XL w/ autoride was the Best ride I’ve ever had on a full size SUV, even over the 08 autoride Denali XL and this Esky ESV.